The transport industry, in particular the aviation and marine sectors, are facing enormous challenges in the upcoming future. Apart from the recent economic and financial crisis, there are challenges such as security of fuel supply, meeting emission requirements and environmental restrictions. From the aviation industry's perspective, the biggest challenge of all is how the industry can continue at its current growth rate of over 5% per year while reducing their share of the carbon dioxide (CO2) emissions.
Globally, the aviation sector produces about 2% of manmade carbon dioxide, according to the IPCC. But with the forecast growth in demand for air services from commercial passengers, air cargo to military, their emissions will grow if cleaner actions are not taking place. As a consequence, the aviation industry has developed a set of ambitions targets aimed at limiting its climate impact while enabling it to continue to provide a key vehicle for economic growth. The targets include (1) the improvement of fleet fuel efficiency by 1.5% per year until 2020; (2) capping net aviation CO2 emissions from 2020; (3) and to halve all aviation CO2 emissions by 2050, compared to 2005.
It is clear that their targets will not be met by technical or operational improvements within the aviation industry alone, nor with just improvements to air traffic control infrastructure and management. These effects can, however, help meet the industry target only with the use of low-carbon, sustainable aviation fuels, such as bio-fuels or biosynthetic fuels.
Aviation has no alternative to liquid fuels for the foreseeable future, unlike ground transportation or power generation, which have had a choice of energy success (such as hybrid technology, batteries, wind or solar). Aviation must, therefore, aim to replace fossil-based petroleum fuels with lower carbon alternatives such as second generation advanced bio synthetic fuels.
The first generation of biofuels has been highly criticized for its negative impact on both people and the environment. Food price issues, land and water use and pollution have all been of great concern. Furthermore, the aviation industry is technically unable to use many of these first generation fuels. Ethanol freezes at the high altitudes at which jet turbines operate (−50° C.) and biodiesel does not carry the required energy density.
Safety is the most important aspect of aircraft systems, closely followed by its economic performance. Since commercial aviation started, the reliability of engines and jet propulsion systems have continuously improved, and today a modern jet aircraft has an engine failure rate less than 0.002/1000 hrs. This is dependent on an extremely reliable propulsion system with every component, including the fuel, to meet very specific requirements. The safety issues and cost aspects impose very strict regulations and requirements on the fuel that is used for aircraft engines.
Jet engine fuel is kerosene, lighter than diesel and heavier than gasoline. Jet fuel comes in different versions or according to different standards. For commercial aviation, the fuel is named Jet A-1, Jet-A or sometimes AVTUR (Aviation Turbine Fuel). The standards ASTM D1655 (US) and Defense Standard 91-91 (UK) prescribes properties of the fuel, such as freezing point, ignition point, boiling point and several (features) specifications of the fuel must be observed. Altogether, the strict specifications for aviation fuel substantially raises the bar for what can be used in real flights compared to land transport systems.
The aviation biofuels will have to, therefore, be “drop-in”, i.e., virtually identical to the Jet A-1 fuel. This means that it can be “dropped” into the current fuel supply. The only synthetic paraffinic kerosene (SPK) produced by a Fischer Tropsch process meets and exceeds all the required specifications of Jet A1 and can therefore be blended on a 50/50 mix to meet ASTM and Defense Standard specifications. Furthermore, airlines have been using blends of FT fuels for many years with no engine or safety issues particularly in South Africa.